Hydraulic Shock-Absorber, Particularly for a Vehicle Suspension, With Two Compression Valves

A hydraulic shock-absorber comprising

• an outer cylindrical tube extending along a longitudinal axis (z),
• an inner cylindrical tube coaxial with the outer cylindrical tube and defining with the outer cylindrical tube an annular chamber filled in a top portion thereof with a compressible fluid,
• a rod arranged coaxially with the outer cylindrical tube and the inner cylindrical tube and partially protruding from the top end of the outer cylindrical tube and of the inner cylindrical tube,
• a main piston slidably mounted in the inner cylindrical tube along said longitudinal axis (z) and fixed to the rod, the main piston dividing an inner volume of the inner cylindrical tube into an extension chamber and a compression chamber, both containing a damping fluid,
• a valve assembly mounted on a bottom wall of the inner cylindrical tube and comprising a first compression valve configured as a non-return valve allowing flow of the damping fluid only in a direction from the compression chamber to the annular chamber during a compression phase of the shock-absorber and a first intake valve configured as a non-return valve allowing the flow of the damping fluid only in the direction from the annular chamber to the compression chamber during an extension phase of the shock-absorber, wherein said first compression valve comprises at least one first closure element, that keeps at least one first through hole provided in the bottom wall of the inner cylindrical tube normally closed and to deform or displace elastically, from a given pressure value in the compression chamber, to allow flow of the damping fluid through said at least one first through hole from the compression chamber to the annular chamber,
• a cup-shaped body mounted in the inner cylindrical tube, coaxially therewith, inside the compression chamber, and
• an auxiliary piston rigidly connected to the main piston and slidably disposed in the cup-shaped body at least during a final section of the compression phase of the shock-absorber,
• wherein the cup-shaped body comprises a lateral wall, separate from the inner cylindrical tube, and a bottom wall, said lateral wall and said bottom wall defining, together with the auxiliary piston, a working chamber wherein the damping fluid is compressed by the auxiliary piston when the auxiliary piston slides in the cup-shaped body towards the bottom wall,
• wherein the cup-shaped body further comprises a second compression valve configured as a non-return valve allowing flow of the damping fluid only in the direction from the working chamber of the cup-shaped body towards a lower portion of the compression chamber comprised between the bottom wall of the cup-shaped body and the bottom wall of the inner cylindrical tube,
• wherein said second compression valve comprises at least one second closure element that keeps at least one second through hole provided in the bottom wall of the cup-shaped body normally closed and to deform or displace elastically, from a given pressure value in the working chamber of the cup-shaped body, to allow the flow of the damping fluid through said at least one second through hole from the working chamber to said lower portion of the compression chamber, and
• wherein said at least one second closure element is arranged outside the cup-shaped body, underneath the bottom wall of the cup-shaped body.